1. Field of the Invention
The present invention relates generally to the field of devices for holding a large display screen in a rolled-up condition while allowing the screen to be extended therefrom.
2. Description of the Prior Art
A large screen portable LED display is disclosed in International Application No. PCT/US2009/063884, the associated International Publication No. WO2010/054380 and International Application No. PCT/US2012/0002357 which are hereby incorporated by reference in their entirety. In the PCT application, a large screen display includes a plurality of rigid segments containing LEDs. The rigid segments are linked by hinges or cables so the display is flexible and can be rolled up for storage and transport. The display can then be unrolled and extended from a protective container.
Large screen displays may be suspended from the ceiling or other structure for use at sporting events and other public gatherings. During use, the screen is deployed downwardly whereas it may be rolled upwardly into the container when not in use thereby protecting the display screen. Significant problems exist concerning the mechanism for unwinding and winding up the screen. For example, many screens weigh in excess of 1,500 pounds and extend wrappingly around a long wind-up axle. In some cases, the axle may have a length of 10 feet or more. Thus, if the winding force is applied directly to the axle, the axle may twist causing delayed movement, jamming, and even eventual failure of the axle. In lieu of locating the driving axle of the driver motor along the same axis of rotation as the axis of rotation of the wind up mechanism, I have located the motor and its output axle outwardly of the wind up mechanism axis of rotation thereby providing a mechanical advantage. Disclosed herein is a drum surrounding the wind up axle with the wind up force being applied through the drum outwardly of the axle eliminating axle twisting, and also providing a mechanical advantage when winding the drum allowing for a small driver motor.
The device disclosed herein further includes a truss surrounding the rotatable drum with the large screen display wrapped on the drum and extendable therefrom. The weight of the large screen display is directed through the drum axle to a pair of bearings mounted to plates fixedly secured to a truss. Likewise, the forces directed from the drum during the winding process are directed through a driving sprocket to the truss.
A further problem of the prior art screen display wind up mechanism relates to the routing of the electrical cable connecting the displays, LEDs, etc. to the incoming source of data and power located outwardly of the wind up mechanism. Due to the high frequency of the incoming data, unacceptable results are obtained when using a slip ring type of cable connector connecting the cable exiting the wind up mechanism to the external source of data and power. It is therefore necessary to use a non-sliding connection. The result of using a non-sliding type of connection is the possible twisting of the cable during rotation of the wind-up drum during either extension or retraction of the large screen display. Disclosed herein is a cable that exits the wind up mechanism through the drum end and driving sprocket and moves therewith. The cable spirals around the axis of rotation a sufficient number of turns to prevent the twisting and snarling of the cable.